1. Impervious Cover and Erosion: Brushy Creek, Round Rock, Texas GRG 360-G Spring 2004 Beau Barnett Brett Franco

2. Erosion and Soil Loss Due to the Increase in Impervious Cover Increase in impervious cover can have detrimental effects on soil loss and stream erosion. Soil Infiltration rate goes down with more impervious cover. Runoff increases when there is less soil infiltration. With more runoff, the chance for greater soil loss increases

3. Area of Study Round Rock, Texas Williamson County Brushy Creek

4. Population Boom of Round Rock From 1990 to 2000, population of Round Rock has more than doubled. 1994 Dell Computers moved it’s headquarters from Austin to Round Rock, creating over 10,000 jobs for the area. With an increase in population, rapid urbanization occurred.

5. Methods Used for Analysis Delineation of Brushy Creek and morphometric analysis using ArcHydro Model soil erosion and soil loss using the Revised Universal Soil Loss Equation (RUSLE) Digitizing zones of impervious cover and area analysis using the Field Calculator

6. Sources Secondary Data: 30 meter DEMs from TNRIS 2.5 meter DOQQs for Round Rock, Texas Annual Rainfall Data for Round Rock, Texas

7. Techniques Revised Universal Soil Loss Equation (RUSLE) A = R * K * LS * C * P A = estimated average soil loss in tons per acre per year R = rainfall-runoff erosivity factor K = soil erodibility factor L = slope length factor S = slope steepness factor C = cover-management factor P = support practice factor

8. RUSLE Factors R = 94 Estimated value from tamu.edu K = 0.5 Estimated value due to rocky sandy soils LS = Grid derived from slope and flow accumulation C = 0.75 for West Brushy Creek, 0.35 for East Brushy Creek Value based on percentage of impervious cover in basin P = 1 Value constant due to size of study area

12. Sources of Error More recent DOQQs Imprecise soil data for K factor C factor is not constant on a landscape RUSLE equation is a model, not an exact science!

13. Future Research Better defined factors for RUSLE equation More widely available data Study amount of soil deposition downstream Development of environmentally sensitive construction practices Use of newly developed pervious concrete

14. Conclusions With the relocation of Dell causing a population boom in Round Rock the amount of impervious cover increased greatly. This in turn increased runoff and soil erosion in the area and measures need to be taken to lessen the impacts of this urban sprawl.

15. Works Cited http://www.tnris.state.tx.us http://www.iwr.msu.edu/rusle/ http://www.dell.com/ http://www.ci.round-rock.tx.us http://www.utexas.edu/depts/grg/hudson/grg360g/EGIS/E_grg360g.htm